Superconductivity in a quintuple-layer square-planar nickelate

TL;DR

Researchers synthesized a new quintuple-layer nickelate, Nd$_6$Ni$_5$O$_{12}$, which exhibits superconductivity around 13 K, expanding the family of tunable nickelate superconductors and bridging behaviors between cuprates and infinite-layer nickelates.

Contribution

First synthesis of the Nd$_6$Ni$_5$O$_{12}$ nickelate with superconductivity, demonstrating a new family of tunable superconducting nickelates bridging cuprate and infinite-layer behaviors.

Findings

Superconductivity observed at ~13 K in Nd$_6$Ni$_5$O$_{12}$.

Electronic structure shows interpolation between cuprate-like and nickelate-like behavior.

Square-planar nickelates identified as a new tunable superconductor family.

Abstract

Since the discovery of high-temperature superconductivity in the copper oxide materials, there have been sustained efforts to both understand the origins of this phase and discover new cuprate-like superconducting materials. One prime materials platform has been the rare-earth nickelates and indeed superconductivity was recently discovered in the doped compound Nd$_{0.8}$Sr$_{0.2}$NiO$_2$. Undoped NdNiO$_2$ belongs to a series of layered square-planar nickelates with chemical formula Nd$_{n+1}$Ni$_n$O$_{2n+2}$ and is known as the 'infinite-layer' ($n = \infty$) nickelate. Here, we report the synthesis of the quintuple-layer ($n = 5$) member of this series, Nd$_6$Ni$_5$O$_{12}$, in which optimal cuprate-like electron filling ($d^{8.8}$) is achieved without chemical doping. We observe a superconducting transition beginning at $\sim$13 K. Electronic structure calculations, in tandem with magnetoresistive and spectroscopic measurements, suggest that Nd$_6$Ni$_5$O$_{12}$ interpolates between cuprate-like and infinite-layer nickelate-like behavior. In engineering a distinct superconducting nickelate, we identify the square-planar nickelates as a new family of superconductors which can be tuned via both doping and dimensionality.